Theory, technique, and practice of magnetic resonance angiography

The morphology of the human cerebrovascular system

While several methodologies exist for quantifying gray and white matter properties in humans, relatively little is known regarding the spatial organization and the intersubject variability of cerebral vessels. To resolve this, we developed a fast, open-source processing algorithm using advanced vessel segmentation schemes and iterative nonlinear registration to isolate, extract, and quantify cerebral vessels in susceptibility weighting imaging (SWI) and time-of-flight angiography (TOF-MRA) datasets acquired in a large cohort (n = 42) of healthy individuals. From this, whole-brain venous and arterial probabilistic maps were generated along with the computation of regional densities and diameters within regions based on popular anatomical and functional atlases. The results show that cerebral vasculature is highly heterogeneous, displaying disproportionally large vessel densities in brain areas such as the anterior and posterior cingulate, cuneus, precuneus, parahippocampus, insula, and temporal gyri. On average, venous densities were slightly higher and less variable across subjects than arterial. Moreover, regional variations in both venous and arterial density were significantly correlated to cortical thickness (R = 0.42). This publicly available new atlas of the human cerebrovascular system provides a first step toward quantifying morphological changes in the diseased brain and serving as a potential regression tool in fMRI analysis.

Dying art of a history and physical: pulsatile tinnitus

Modern medicine often leaves the history and physical by the wayside. Physicians instead skip directly to diagnostic modalities like MRI and angiography. In this case report, we discuss a patient who presented with migraine symptoms. Auscultation revealed signs of pulsatile tinnitus. Further imaging concluded that it was secondary to a type I dural arteriovenous fistula. Thanks to a proper and thorough history and physical, the patient was streamlined into an accurate and efficient work-up leading to symptomatic relief and quality of life improvement. Imaging is a powerful adjunctive technique in modern medicine, but physicians must not rely on machines to diagnose their patients. If this trend continues, it will have a tremendous negative impact on the cost and calibre of healthcare. Our hope is that this case will spread awareness in the medical community, urging physicians to use the lost art of a history and physical.